I don't drive the highway much, so I would say my driving is 80% city, 20% highway.

I was getting 27 mpg city. Now, I'm getting 32 in the city with a K&N air filter installed. Best $35 ever. I'm nearing 390 miles to a tank of gas solely off driving in the city. Yes, it's also a manual.

NO WAY does dropping in a K&N filter get you a 5 mpg gain. I've put in K&N's in several cars and never realized any economy gain. Even K&N is smart enough to not make any fuel economy claims in their marketing.

K&N: "A lot of exaggerated claims are made in the marketplace by products claiming to improve gas mileage. K&N makes no general fuel economy claims, however we encourage you to try our air filter for yourself. Keeping air filter restriction as low as possible can be an important tool, among others, for maintaining high mileage."